The title was created because the two brothers' spheres of influence were over the spirit. Irmo was the master of visions and dreams, Námo had power over the fëar of Elves and Men who gathered in his halls after death, where the fëar of the Elves abode while those of Men left the Circles of the World. Námo delivered judgement on Manwë's bidding in serious matters (such as the Doom of the Noldor) but also judged over the fate of the elvish fëar.